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@ -1,6 +1,6 @@ |
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/* Copyright 1998 by the Massachusetts Institute of Technology.
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* Copyright (C) 2004-2012 by Daniel Stenberg |
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* Copyright (C) 2004-2013 by Daniel Stenberg |
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* |
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* Permission to use, copy, modify, and distribute this |
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* software and its documentation for any purpose and without |
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@ -17,9 +17,6 @@ |
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#include "ares_setup.h" |
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#ifdef HAVE_SYS_SOCKET_H |
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# include <sys/socket.h> |
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#endif |
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#ifdef HAVE_SYS_UIO_H |
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# include <sys/uio.h> |
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#endif |
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@ -41,16 +38,9 @@ |
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# include <arpa/nameser_compat.h> |
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#endif |
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#ifdef HAVE_SYS_TIME_H |
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# include <sys/time.h> |
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#endif |
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#ifdef HAVE_STRINGS_H |
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# include <strings.h> |
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#endif |
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#ifdef HAVE_UNISTD_H |
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# include <unistd.h> |
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#endif |
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#ifdef HAVE_SYS_IOCTL_H |
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# include <sys/ioctl.h> |
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#endif |
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@ -59,10 +49,7 @@ |
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#endif |
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#include <assert.h> |
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#include <string.h> |
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#include <stdlib.h> |
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#include <fcntl.h> |
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#include <time.h> |
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#include "ares.h" |
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#include "ares_dns.h" |
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@ -356,11 +343,11 @@ static void read_tcp_data(ares_channel channel, fd_set *read_fds, |
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} |
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if(read_fds) |
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/* If there's an error and we close this socket, then open
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* another with the same fd to talk to another server, then we |
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* don't want to think that it was the new socket that was |
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* ready. This is not disastrous, but is likely to result in |
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* extra system calls and confusion. */ |
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/* If there's an error and we close this socket, then open another
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* with the same fd to talk to another server, then we don't want to |
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* think that it was the new socket that was ready. This is not |
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* disastrous, but is likely to result in extra system calls and |
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* confusion. */ |
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FD_CLR(server->tcp_socket, read_fds); |
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if (server->tcp_lenbuf_pos != 2) |
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@ -430,7 +417,7 @@ static void read_udp_packets(ares_channel channel, fd_set *read_fds, |
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struct server_state *server; |
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int i; |
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ssize_t count; |
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unsigned char buf[PACKETSZ + 1]; |
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unsigned char buf[MAXENDSSZ + 1]; |
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#ifdef HAVE_RECVFROM |
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ares_socklen_t fromlen; |
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union { |
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@ -472,25 +459,31 @@ static void read_udp_packets(ares_channel channel, fd_set *read_fds, |
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/* To reduce event loop overhead, read and process as many
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* packets as we can. */ |
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do { |
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if (server->udp_socket == ARES_SOCKET_BAD) |
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count = 0; |
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else { |
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#ifdef HAVE_RECVFROM |
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if (server->addr.family == AF_INET) |
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fromlen = sizeof(from.sa4); |
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else |
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fromlen = sizeof(from.sa6); |
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count = (ssize_t)recvfrom(server->udp_socket, (void *)buf, sizeof(buf), |
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0, &from.sa, &fromlen); |
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count = (ssize_t)recvfrom(server->udp_socket, (void *)buf, |
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sizeof(buf), 0, &from.sa, &fromlen); |
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#else |
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count = sread(server->udp_socket, buf, sizeof(buf)); |
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#endif |
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} |
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if (count == -1 && try_again(SOCKERRNO)) |
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continue; |
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else if (count <= 0) |
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handle_error(channel, i, now); |
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#ifdef HAVE_RECVFROM |
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else if (!same_address(&from.sa, &server->addr)) |
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/* The address the response comes from does not match
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* the address we sent the request to. Someone may be |
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* attempting to perform a cache poisoning attack. */ |
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/* The address the response comes from does not match the address we
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* sent the request to. Someone may be attempting to perform a cache |
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* poisoning attack. */ |
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break; |
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#endif |
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else |
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@ -507,11 +500,10 @@ static void process_timeouts(ares_channel channel, struct timeval *now) |
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struct list_node* list_head; |
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struct list_node* list_node; |
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/* Process all the timeouts that have fired since the last time we
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* processed timeouts. If things are going well, then we'll have |
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* hundreds/thousands of queries that fall into future buckets, and |
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* only a handful of requests that fall into the "now" bucket, so |
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* this should be quite quick. |
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/* Process all the timeouts that have fired since the last time we processed
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* timeouts. If things are going well, then we'll have hundreds/thousands of |
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* queries that fall into future buckets, and only a handful of requests |
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* that fall into the "now" bucket, so this should be quite quick. |
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*/ |
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for (t = channel->last_timeout_processed; t <= now->tv_sec; t++) |
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{ |
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@ -536,7 +528,7 @@ static void process_answer(ares_channel channel, unsigned char *abuf, |
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int alen, int whichserver, int tcp, |
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struct timeval *now) |
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{ |
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int tc, rcode; |
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int tc, rcode, packetsz; |
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unsigned short id; |
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struct query *query; |
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struct list_node* list_head; |
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@ -553,11 +545,10 @@ static void process_answer(ares_channel channel, unsigned char *abuf, |
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rcode = DNS_HEADER_RCODE(abuf); |
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/* Find the query corresponding to this packet. The queries are
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* hashed/bucketed by query id, so this lookup should be quick. |
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* Note that both the query id and the questions must be the same; |
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* when the query id wraps around we can have multiple outstanding |
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* queries with the same query id, so we need to check both the id and |
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* question. |
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* hashed/bucketed by query id, so this lookup should be quick. Note that |
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* both the query id and the questions must be the same; when the query id |
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* wraps around we can have multiple outstanding queries with the same query |
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* id, so we need to check both the id and question. |
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*/ |
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query = NULL; |
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list_head = &(channel->queries_by_qid[id % ARES_QID_TABLE_SIZE]); |
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@ -574,11 +565,34 @@ static void process_answer(ares_channel channel, unsigned char *abuf, |
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if (!query) |
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return; |
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packetsz = PACKETSZ; |
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/* If we use EDNS and server answers with one of these RCODES, the protocol
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* extension is not understood by the responder. We must retry the query |
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* without EDNS enabled. |
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*/ |
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if (channel->flags & ARES_FLAG_EDNS) |
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{ |
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packetsz = channel->ednspsz; |
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if (rcode == NOTIMP || rcode == FORMERR || rcode == SERVFAIL) |
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{ |
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int qlen = alen - EDNSFIXEDSZ; |
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channel->flags ^= ARES_FLAG_EDNS; |
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query->tcplen -= EDNSFIXEDSZ; |
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query->qlen -= EDNSFIXEDSZ; |
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query->tcpbuf[0] = (unsigned char)((qlen >> 8) & 0xff); |
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query->tcpbuf[1] = (unsigned char)(qlen & 0xff); |
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DNS_HEADER_SET_ARCOUNT(query->tcpbuf + 2, 0); |
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query->tcpbuf = realloc(query->tcpbuf, query->tcplen); |
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ares__send_query(channel, query, now); |
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return; |
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} |
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} |
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/* If we got a truncated UDP packet and are not ignoring truncation,
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* don't accept the packet, and switch the query to TCP if we hadn't |
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* done so already. |
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*/ |
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if ((tc || alen > PACKETSZ) && !tcp && !(channel->flags & ARES_FLAG_IGNTC)) |
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if ((tc || alen > packetsz) && !tcp && !(channel->flags & ARES_FLAG_IGNTC)) |
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{ |
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if (!query->using_tcp) |
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{ |
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@ -591,8 +605,8 @@ static void process_answer(ares_channel channel, unsigned char *abuf, |
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/* Limit alen to PACKETSZ if we aren't using TCP (only relevant if we
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* are ignoring truncation. |
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*/ |
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if (alen > PACKETSZ && !tcp) |
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alen = PACKETSZ; |
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if (alen > packetsz && !tcp) |
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alen = packetsz; |
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/* If we aren't passing through all error packets, discard packets
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* with SERVFAIL, NOTIMP, or REFUSED response codes. |
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@ -626,6 +640,31 @@ static void process_broken_connections(ares_channel channel, |
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} |
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} |
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/* Swap the contents of two lists */ |
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static void swap_lists(struct list_node* head_a, |
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struct list_node* head_b) |
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{ |
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int is_a_empty = ares__is_list_empty(head_a); |
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int is_b_empty = ares__is_list_empty(head_b); |
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struct list_node old_a = *head_a; |
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struct list_node old_b = *head_b; |
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if (is_a_empty) { |
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ares__init_list_head(head_b); |
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} else { |
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*head_b = old_a; |
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old_a.next->prev = head_b; |
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old_a.prev->next = head_b; |
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} |
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if (is_b_empty) { |
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ares__init_list_head(head_a); |
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} else { |
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*head_a = old_b; |
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old_b.next->prev = head_a; |
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old_b.prev->next = head_a; |
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} |
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} |
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static void handle_error(ares_channel channel, int whichserver, |
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struct timeval *now) |
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{ |
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@ -639,15 +678,14 @@ static void handle_error(ares_channel channel, int whichserver, |
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/* Reset communications with this server. */ |
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ares__close_sockets(channel, server); |
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/* Tell all queries talking to this server to move on and not try
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* this server again. We steal the current list of queries that were |
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* in-flight to this server, since when we call next_server this can |
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* cause the queries to be re-sent to this server, which will |
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* re-insert these queries in that same server->queries_to_server |
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* list. |
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/* Tell all queries talking to this server to move on and not try this
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* server again. We steal the current list of queries that were in-flight to |
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* this server, since when we call next_server this can cause the queries to |
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* be re-sent to this server, which will re-insert these queries in that |
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* same server->queries_to_server list. |
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*/ |
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ares__init_list_head(&list_head); |
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ares__swap_lists(&list_head, &(server->queries_to_server)); |
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swap_lists(&list_head, &(server->queries_to_server)); |
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for (list_node = list_head.next; list_node != &list_head; ) |
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{ |
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query = list_node->data; |
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@ -663,14 +701,15 @@ static void handle_error(ares_channel channel, int whichserver, |
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} |
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static void skip_server(ares_channel channel, struct query *query, |
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int whichserver) { |
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/* The given server gave us problems with this query, so if we have
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* the luxury of using other servers, then let's skip the |
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* potentially broken server and just use the others. If we only |
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* have one server and we need to retry then we should just go ahead |
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* and re-use that server, since it's our only hope; perhaps we |
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* just got unlucky, and retrying will work (eg, the server timed |
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* out our TCP connection just as we were sending another request). |
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int whichserver) |
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{ |
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/* The given server gave us problems with this query, so if we have the
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* luxury of using other servers, then let's skip the potentially broken |
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* server and just use the others. If we only have one server and we need to |
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* retry then we should just go ahead and re-use that server, since it's our |
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* only hope; perhaps we just got unlucky, and retrying will work (eg, the |
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* server timed out our TCP connection just as we were sending another |
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* request). |
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*/ |
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if (channel->nservers > 1) |
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{ |
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@ -693,11 +732,10 @@ static void next_server(ares_channel channel, struct query *query, |
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query->server = (query->server + 1) % channel->nservers; |
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server = &channel->servers[query->server]; |
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/* We don't want to use this server if (1) we decided this
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* connection is broken, and thus about to be closed, (2) |
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* we've decided to skip this server because of earlier |
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* errors we encountered, or (3) we already sent this query |
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* over this exact connection. |
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/* We don't want to use this server if (1) we decided this connection is
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* broken, and thus about to be closed, (2) we've decided to skip this |
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* server because of earlier errors we encountered, or (3) we already |
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* sent this query over this exact connection. |
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*/ |
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if (!server->is_broken && |
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!query->server_info[query->server].skip_server && |
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@ -709,11 +747,11 @@ static void next_server(ares_channel channel, struct query *query, |
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return; |
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} |
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/* You might think that with TCP we only need one try. However,
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* even when using TCP, servers can time-out our connection just |
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* as we're sending a request, or close our connection because |
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* they die, or never send us a reply because they get wedged or |
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* tickle a bug that drops our request. |
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/* You might think that with TCP we only need one try. However, even
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* when using TCP, servers can time-out our connection just as we're |
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* sending a request, or close our connection because they die, or never |
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* send us a reply because they get wedged or tickle a bug that drops |
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* our request. |
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*/ |
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} |
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@ -749,11 +787,11 @@ void ares__send_query(ares_channel channel, struct query *query, |
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end_query(channel, query, ARES_ENOMEM, NULL, 0); |
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return; |
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} |
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/* To make the common case fast, we avoid copies by using the
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* query's tcpbuf for as long as the query is alive. In the rare |
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* case where the query ends while it's queued for transmission, |
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* then we give the sendreq its own copy of the request packet |
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* and put it in sendreq->data_storage. |
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/* To make the common case fast, we avoid copies by using the query's
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* tcpbuf for as long as the query is alive. In the rare case where the |
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* query ends while it's queued for transmission, then we give the |
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* sendreq its own copy of the request packet and put it in |
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* sendreq->data_storage. |
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*/ |
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sendreq->data_storage = NULL; |
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sendreq->data = query->tcpbuf; |
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@ -916,10 +954,12 @@ static int configure_socket(ares_socket_t s, int family, ares_channel channel) |
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} |
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} |
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else if (family == AF_INET6) { |
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if (memcmp(channel->local_ip6, &ares_in6addr_any, sizeof(channel->local_ip6)) != 0) { |
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if (memcmp(channel->local_ip6, &ares_in6addr_any, |
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sizeof(channel->local_ip6)) != 0) { |
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memset(&local.sa6, 0, sizeof(local.sa6)); |
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local.sa6.sin6_family = AF_INET6; |
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memcpy(&local.sa6.sin6_addr, channel->local_ip6, sizeof(channel->local_ip6)); |
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memcpy(&local.sa6.sin6_addr, channel->local_ip6, |
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sizeof(channel->local_ip6)); |
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if (bind(s, &local.sa, sizeof(local.sa6)) < 0) |
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return -1; |
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} |
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@ -1222,19 +1262,17 @@ static void end_query (ares_channel channel, struct query *query, int status, |
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assert(sendreq->data_storage == NULL); |
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if (status == ARES_SUCCESS) |
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{ |
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/* We got a reply for this query, but this queued
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* sendreq points into this soon-to-be-gone query's |
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* tcpbuf. Probably this means we timed out and queued |
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* the query for retransmission, then received a |
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* response before actually retransmitting. This is |
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* perfectly fine, so we want to keep the connection |
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* running smoothly if we can. But in the worst case |
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* we may have sent only some prefix of the query, |
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* with some suffix of the query left to send. Also, |
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* the buffer may be queued on multiple queues. To |
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* prevent dangling pointers to the query's tcpbuf and |
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* handle these cases, we just give such sendreqs |
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* their own copy of the query packet. |
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/* We got a reply for this query, but this queued sendreq
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* points into this soon-to-be-gone query's tcpbuf. Probably |
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* this means we timed out and queued the query for |
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* retransmission, then received a response before actually |
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* retransmitting. This is perfectly fine, so we want to keep |
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* the connection running smoothly if we can. But in the worst |
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* case we may have sent only some prefix of the query, with |
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* some suffix of the query left to send. Also, the buffer may |
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* be queued on multiple queues. To prevent dangling pointers |
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* to the query's tcpbuf and handle these cases, we just give |
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* such sendreqs their own copy of the query packet. |
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*/ |
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sendreq->data_storage = malloc(sendreq->len); |
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if (sendreq->data_storage != NULL) |
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@ -1245,14 +1283,12 @@ static void end_query (ares_channel channel, struct query *query, int status, |
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} |
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if ((status != ARES_SUCCESS) || (sendreq->data_storage == NULL)) |
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{ |
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/* We encountered an error (probably a timeout,
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* suggesting the DNS server we're talking to is |
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* probably unreachable, wedged, or severely |
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* overloaded) or we couldn't copy the request, so |
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* mark the connection as broken. When we get to |
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* process_broken_connections() we'll close the |
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* connection and try to re-send requests to another |
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* server. |
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/* We encountered an error (probably a timeout, suggesting the
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* DNS server we're talking to is probably unreachable, |
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* wedged, or severely overloaded) or we couldn't copy the |
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* request, so mark the connection as broken. When we get to |
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* process_broken_connections() we'll close the connection and |
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* try to re-send requests to another server. |
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*/ |
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server->is_broken = 1; |
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/* Just to be paranoid, zero out this sendreq... */ |
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@ -1266,8 +1302,8 @@ static void end_query (ares_channel channel, struct query *query, int status, |
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query->callback(query->arg, status, query->timeouts, abuf, alen); |
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ares__free_query(query); |
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/* Simple cleanup policy: if no queries are remaining, close all
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* network sockets unless STAYOPEN is set. |
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/* Simple cleanup policy: if no queries are remaining, close all network
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* sockets unless STAYOPEN is set. |
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*/ |
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if (!(channel->flags & ARES_FLAG_STAYOPEN) && |
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ares__is_list_empty(&(channel->all_queries))) |
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Ben Noordhuis
12 years ago